[maverick]

I doubt it would be a head end problem if your friends connection is fine,assuming they are in the same area as yourself.

Are your friends in the same post code area?

Are there any neighbours the closer the better with ntl broadband to see how their coneenction is.
It could be a cabling problem from the node in the street to your property,if it is then a cable repull is needed.

Let us know how you get on.